1. Field
This invention pertains to carbon sequestration. In particular, it pertains to a method to create a net increase in soil organic carbon (SOC) by acidifying land applied waters with pH adjusted sulfur dioxide to open up soil pores while providing nutrients to plants and soil bacteria, which assimilate carbon dioxide.
2. State of the Art
Carbon (C) sequestration refers to the storage of carbon into a stable form. This act of sequestering carbon is dependent upon the nature of the carbon sink and can be achieved by several ways: directly by inorganic chemical reactions that cause carbon dioxide (CO2) in the form of carbonates/bicarbonates to bond with dissolved minerals and salts to form compounds such as calcium and magnesium carbonates; by plant photosynthesis, which uses sunlight to combine carbon dioxide (CO2) from the air and water (H2O) to form glucose (C6H12O6), a simple sugar that is stored within the tissue of living plants; and indirectly, by the microbial decomposition of the biomass of plant and animal tissue into other compounds such as carbohydrates, proteins, organic acids, humic substances, waxes, coal, oil, and natural gas, etc. Combined together, these organic compounds essentially act to “hold soil together”, and is how soil attains its fertility. The higher the content of SOC, the greater the fertility and productivity of the soil. Soil microbes comprise bacteria, algae, viruses, actinomycetes, and protozoia. Fungi are generally multi-celled organisms, but will hereinafter be included in the term soil micro-organisms, or microbes, for short.
Microbes are classified as autotrophs, which derive their energy from the sun through photosynthesis or chemical reactions. Autotrophs fix carbon dioxide to make their own food source, which may be fueled by light energy (photoautotrophic), or by oxidation of nitrogen, sulfur, or other elements (chemoautotrophic). While chemoautotrophs are uncommon, photoautotrophs are common and quite diverse. Chemoautotrophs include the cyanobacteria, green sulfur bacteria, purple sulfur bacteria, and purple nonsulfur bacteria. The sulfur bacteria are particularly interesting, since they use hydrogen sulfide as hydrogen donor, instead of water like most other photosynthetic organisms, including cyanobacteria.
All other microbes are called heterotrophs, which get their energy from consuming the fixed carbon in living and dead organisms. Some are aerobic requiring oxygen for metabolism, and others are anaerobic, which do not. Most bacteria may be placed into one of three groups based on their response to gaseous oxygen. Aerobic bacteria thrive in the presence of oxygen and require it for their continued growth and existence. Other bacteria are anaerobic, and cannot tolerate gaseous oxygen, such as those bacteria which live in deep underwater sediments, or those which cause bacterial food poisoning. The third group is the facultative anaerobes, which prefer growing in the presence of oxygen, but can continue to grow without it.
Carbon is recycled aerobically where plants and soil microbes photosynthesize the carbon dioxide and make organic compounds, such as sugars. Other chemo-lithiotropic bacteria can assimilate carbon dioxide in the dark. Certain bacteria are also capable of anaerobic carbon cycling. Chemo-organotrophic microbes break down organic material to release carbon dioxide for plant or microbe photosynthesis. Some saprobic bacteria microbes break down the organic material through fermentation or respiration reactions producing carbon dioxide, methane, and hydrogen, which methane oxidizing bacteria assimilate to produce sugars and amino acids. Thus carbon dioxide is released from and assimilated into soils by various soil microbes and plants.
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, the pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. A diagram of the entire carbon cycle and the carbon dioxide interchange between carbon sinks can be found at http://www.uwsp.edu/geO/faculty/ritter/geog1 . . . . The diagram shows the role soils play in sequestering carbon. Soils sequester 1,580 GigaTons of Carbon and respire 60 GigaTons of Carbon annually. Soil organic matter thus holds almost three to four times the amount of carbon as that contained in the atmosphere.
The article in PhysicalGeography.net, Chapter 9: “Introduction to the Biosphere (r) The Carbon Cycle” outlines how carbon dioxide in various forms is circulated between and contained in various carbon sinks:
SinkAmount in Billions of Metric TonsAtmosphere578 (as of 1700)-766 (as of 1999)Soil Organic Matter1500 to 1600Ocean38,000 to 40,000Marine Sediments and Sedimentary 66,000,000 to 100,000,000RocksTerrestrial Plants540 to 610Fossil Fuel Deposits4000This large soil carbon sink is the only practical method of sequestering carbon as oceans and sediments are difficult to access and adapt for this purpose.
In an effort to sequester more atmospheric carbon into soil organic matter, the Soil Science Society of America, the American Society of Agronomy, and other world scientific organizations have relied and advocated for farmers to grow crops using practices that include: no till or reduced tillage; crop rotation; the use of cover crops; fertility management; and water management (as it pertains to the amount used), etc., as being the “primary tools” and overall strategy to accomplish that goal. While these methods can be helpful and on the “right track”, their ability to sequester more net atmospheric carbon into soil organic carbon, both separately and as a whole, is extremely limited because the actual process of growing crops and supplying the necessary plant biomass itself mechanically disturbs the soil through tilling and aeration to break up bicarbonate buildup. In the process of mechanically disturbing the soil, as for example, tilling the soil to loosen carbonate clogged pores of the soil to increase water soil penetration, the process turns and exposes what soil organic carbon there is and makes it susceptible to erosion and die off through exposure to sunlight, heat, and wind, causing large portions of the soil carbon pool to diminish or become lost.
Land-use changes associated with agriculture can disrupt the natural balance between the production of carbon-containing biomass and the release of carbon by soil respiration. One estimate suggests that this imbalance alone results in an annual net release of CO2 to the atmosphere from agricultural soils equal to about 20 percent of the current annual release of CO2 from the burning of fossil fuels. Agricultural practices in temperate zones, for example, can result in a decline of soil organic matter that ranges from 20 to 40 percent of the original content after about 50 years of cultivation. Although a portion of this loss can be attributed to soil erosion, the majority is from an increased flux of carbon to the atmosphere as CO2. Consequently, more often than not, a net loss of soil carbon results from mechanical tillage methods alone.
Another approach for opening soil pores is to increase carbon sequestration by applying strong mineral acids to break down the carbonate/bicarbonate soil deposits. These strong mineral acids, such as hydrochloric acid, sulfuric acid, and phosphoric acid have no buffering capability, and if not applied in the right dilution actually shock the soil and release CO2 directly into the atmosphere as the soil carbonates/bicarbonates react to the strong acid rather than dissolving as bicarbonates into the aqueous fraction. Low acid pH applications of around 1 to 2 are also damaging to plant roots and soil bacteria so that further uptake of CO2 is adversely affected creating a soil dead zone. In addition, some of these strong mineral acids, such as hydrochloric acid, increase the chloride concentration in the soil exacerbating harmful saline salt buildup. For this reason, use of the current “state of the art” methods provides only “a partial solution” at best, and cannot be relied upon as the sole means to restore and/or sequester more organic carbon back into the soil.
Current methods to sequester carbon re thus inefficient and/or inherently flawed because they do not include the integration of sulfur (S), in a particular form or manner (sulfur dioxide), to increase the population density of microbes within a soil and water solution; and/or as the means to provide and regulate the free hydronium aqueous cation (H3O+) within that system (pH) in order to achieve optimal condition in which the sequestering of carbon can be maximized.
The present method described below recognizes the acid buffering relationship required to adjust the soil carbonate/bicarbonate cycle using the controlled hydronium aqueous cation H3O+ application in conjunction with calcium ion Ca+2 soil pH adjustment to create a sustainable soil condition that will enable plants and soil microbes to optimally photosynthesize and produce the necessary plant and animal biomass which will lead to the acceleration and sequestering of more organic carbon into soil than ever before, such as by promoting deeper root penetration. The present acidification method adapting soils to sequester more carbon is simple to implement, and the net carbon sequestered easy to measure.